U.S. patent number 5,669,653 [Application Number 08/539,356] was granted by the patent office on 1997-09-23 for fluid powered backup tong and method.
This patent grant is currently assigned to Bilco Tools, Inc.. Invention is credited to Dennis J. Penisson.
United States Patent |
5,669,653 |
Penisson |
September 23, 1997 |
Fluid powered backup tong and method
Abstract
The backup tong 10, 110 includes a fluid powered cylinder
assembly 72, 172. A wedge 80, 180 is provided at the end of a
cylinder rod 76, 176 and forces multiple dies into gripping
engagement with the tubular. A pair of links 30, 32 or 130, 132 are
driven laterally outward from the centerline 28, 128 of the tong
body by the wedge 80, 180, thereby forcing the dies to bite the
tubular. The design of the tong is relatively simple and has few
moving parts, yet is highly rugged and dependable. Dies 62, 64 and
66 or 162, 164 and 166 may together provide circumferential
engagement of at least 270.degree. with a tubular, thereby reliably
gripping and minimizing damage to the tubular. The tong 10 includes
a door jaw latch pin 58, and is particularly well suited for use on
dual tubing strings where there is little axial spacing between the
tubing strings.
Inventors: |
Penisson; Dennis J. (Raceland,
LA) |
Assignee: |
Bilco Tools, Inc. (Houma,
LA)
|
Family
ID: |
24150881 |
Appl.
No.: |
08/539,356 |
Filed: |
October 5, 1995 |
Current U.S.
Class: |
294/116; 294/203;
81/57.33 |
Current CPC
Class: |
E21B
19/163 (20130101) |
Current International
Class: |
E21B
19/16 (20060101); E21B 19/00 (20060101); B25B
013/50 () |
Field of
Search: |
;294/86.1,86.3,88,106,115,116
;81/57.15,57.16,57.18,57.19,57.2,57.21,57.33,57.34,57.35 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Drawing, Weatherford 50-001, undated..
|
Primary Examiner: Kramer; Dean
Attorney, Agent or Firm: Browning Bushman
Claims
What is claimed is:
1. A backup tong for gripping engagement with an oilfield tubular,
comprising:
a tong body having a throat for laterally moving the tong body on
and off the oilfield tubular in a direction generally aligned with
a centerline of the tong body;
a first link pivotally mounted to the tong body about a first
pivot;
a second link pivotally mounted to the tong body about a second
pivot;
a first jaw block pivotally mounted to the first link about a third
pivot, the first jaw block supporting a first die thereon for
gripping engagement with the oilfield tubular;
a second jaw block pivotally mounted to the second link about a
fourth pivot, the second jaw block supporting a second die thereon
for gripping engagement with the oilfield tubular;
a hydraulic cylinder assembly mounted on the tong body and having a
cylinder body and a cylinder rod extending from the cylinder body,
the hydraulic cylinder assembly being mounted on the tong body such
that the cylinder rod is movable along the centerline of the tong
body; and
a wedge mounted on the cylinder rod, the wedge having first and
second cam surfaces thereon provided on opposing sides of the
centerline of the tong body for engagement with the first and
second links, respectively, to force the first and second dies into
gripping engagement with the oilfield tubular, each of the first
and second cam surfaces having an initial high cam angle for moving
the dies toward engagement with the tubular, and a subsequent low
cam angle inclined at an angle less than the high cam angle with
respect to the centerline of the tong body for gripping engagement
of the respective first die and the second die with the oilfield
tubular.
2. The backup tong as defined in claim 1, further comprising:
each of the first jaw block and second jaw block being pivotally
movable with respect to the first link and the second link,
respectively, between an open position for laterally receiving the
tong body on the oilfield tubular and a closed position for
retaining the tubular within the tong body; and
a latch device for selectively interconnecting the first and second
jaw blocks.
3. The backup tong as defined in claim 1, wherein the cylinder
assembly is mounted on the tong body such that extension of the
cylinder rod pushes the wedge along the centerline of the tong body
and away from the oilfield tubular.
4. The backup tong as defined in claim 1, wherein:
each of the first and second links is pivotally mounted to a front
portion of the tong body, and the wedge engages a rear end of each
of the first and second links.
5. The backup tong as defined in claim 1, further comprising:
a third jaw block mounted on the tong body and supporting a third
die thereon for gripping engagement with the oilfield tubular.
6. The backup tong as defined in claim 5, wherein a circumferential
gripping length of each of the first die, the second die, and the
third die which engage the oilfield tubular is at least 90.degree.,
such that the dies grippingly engage a total circumference of at
least 270.degree. of the oilfield tubular.
7. The backup tong as defined in claim 5, comprising:
the third jaw block being movable with respect to the tong
body;
the cylinder body being movably mounted with respect to the tong
body; and
the cylinder body acts against the third jaw block for forcing the
third die into gripping engagement with the oilfield tubular.
8. The backup tong as defined in claim 7, further comprising:
a resilient member for positioning between the cylinder body and
the third jaw block, such that compression of the resilient member
forces the third die into gripping engagement with the oilfield
tubular.
9. The backup tong as defined in claim 1, wherein each of the first
and second cam surfaces on the wedge have a cam angle of from
20.degree. to 40.degree. with respect to the centerline of the tong
body.
10. The backup tong as defined in claim 1, further comprising:
a first roller and second roller each mounted on the first and
second link, respectively, for engaging the respective cam surface
on the wedge.
11. A backup tong for gripping engagement with an oilfield tubular,
comprising:
a tong body having a throat for laterally moving the tong body on
and off the oilfield tubular in a direction generally aligned with
a centerline of the tong body, the tong body including upper and
lower spaced apart tong plates;
a first link pivotally mounted to the tong body about a first pivot
and spaced between the upper and the lower tong plates;
a second link pivotally mounted to the tong body about a second
pivot and spaced between the upper and the lower tong plates;
a first jaw block pivotally mounted to the first link about a third
pivot, the first jaw block supporting a first die thereon for
gripping engagement with the oilfield tubular;
a second jaw block pivotally mounted to the second link about a
fourth pivot, the second jaw block supporting a second die thereon
for gripping engagement with the oilfield tubular;
a third jaw block mounted on the tong body between the upper and
the lower tong plates and supporting a third die thereon for
gripping engagement with the oilfield tubular;
a hydraulic cylinder assembly mounted on the tong body between the
upper and the lower tong plates, the hydraulic cylinder assembly
including a cylinder body and a cylinder rod extending from the
cylinder body; and
a wedge mounted on the cylinder rod, the wedge having first and
second cam surfaces thereon for engagement with the first and
second links, respectively.
12. The backup tong as defined in claim 11, further comprising:
each of the first jaw block and second jaw block being pivotally
movable with respect to the first link and the second link,
respectively, between an open position for laterally receiving the
tong body on the oilfield tubular and a closed position for
retaining the tubular within the tong body; and
a latch device for selectively interconnecting the first and second
jaw blocks.
13. The backup tong as defined in claim 12, wherein at least one of
the first jaw block and the second jaw block have a body thickness
between the respective one of the third and fourth pivot and the
latch device which is less than about 2.5 inches, such that the
backup tong may be laterally moved on one string of a dual tubing
string.
14. The backup tong as defined in claim 13, wherein the cylinder
assembly is mounted on the tong body such that extension of the
cylinder rod pushes the wedge along the centerline of the tong body
and away from the oilfield tubular.
15. The backup tong as defined in claim 13, wherein each of the
first and second cam surfaces on the wedge have a cam angle of from
20.degree. to 40.degree. with respect to the centerline of the tong
body.
16. A backup tong for gripping engagement with an oilfield tubular,
comprising:
a tong body having a throat for laterally moving the tong body on
and off the oilfield tubular in a direction generally aligned with
a centerline of the tong body;
a first link pivotally mounted to the tong body about a first
pivot;
a second link pivotally mounted to the tong body about a second
pivot;
a first jaw block pivotally mounted to the first link about a third
pivot, the first jaw block supporting a first die thereon for
gripping engagement with the oilfield tubular;
a second jaw block pivotally mounted to the second link about a
fourth pivot, the second jaw block supporting a second die thereon
for gripping engagement with the oilfield tubular;
a third jaw block mounted on the tong body and supporting a third
die thereon for gripping engagement with the oilfield tubular;
a hydraulic cylinder assembly mounted on the tong body, the
hydraulic cylinder assembly including a cylinder body and a
cylinder rod extending from the cylinder body, and
a wedge mounted on the cylinder rod, the wedge having first and
second cam surfaces thereon for engagement with the first and
second links, respectively.
17. The backup tong as defined in claim 16, wherein the cylinder
assembly is mounted on the tong body such that extension of the
cylinder rod pushes the wedge along the centerline of the tong
body.
18. The backup tong as defined in claim 16, further comprising:
each of the first and second links is pivotally mounted to a front
portion of the tong body, and the wedge engages a rear end of each
of the first and second links; and
a first roller and second roller each mounted on the first and
second link, respectively, for engaging the respective cam surface
on the wedge.
19. The backup tong as defined in claim 16, further comprising:
each of the first jaw block and second jaw block is movable between
an open position for laterally receiving the tong body on the
oilfield tubular and a closed position for retaining the tubular
within the tong body.
20. The backup tong as defined in claim 19, wherein actuation of
the hydraulic cylinder assembly automatically moves each of the
first jaw block and the second jaw block between the open position
and the closed position.
Description
FIELD OF THE INVENTION
The present invention relates to backup tongs of a type commonly
used to grip an oilfield tubular in a string extending into a
hydrocarbon recovery well. More particularly, this invention
relates to a backup tong which includes a wedge powered by a
hydraulic cylinder. The backup tong has relatively few moving
parts, and is well suited for use on a dual tubing string.
BACKGROUND OF THE INVENTION
Backup tongs are well known tools use in hydrocarbon recovery
operations. Rotary tongs typically grip and rotate an upper
oilfield tubular to make up or break apart a threaded connection,
while backup tongs grip the lower oilfield tubular to prevent its
rotation by the power tong. Assuming a lower oilfield tubular is
rotationally fixed, the backup tong frequently provides the
structure which prevents rotation of the power tong. A load cell
between the backup tong and the rotary tong may thus determine the
torque applied to the connection. Manual backup tongs are commonly
employed in oilfield operations, although fluid powered backup
tongs are increasingly used to reduce the time required to make up
and break apart threaded connections. The backup tong ideally
functions to uniformly and reliably grip the tubular without
damaging the tubular due to excessive gripping force. An early
version of a rotating tong cooperating with a backup tong is
disclosed in U.S. Pat. No. 2,639,894.
Prior art backup tongs have used one more hydraulic cylinders to
force dies into gripping engagement with a tubular. U.S. Pat. No.
4,649,777 discloses a backup tong with three gripping dies each
powered by a respective hydraulic cylinder assembly. A wedge
powered by a hydraulic cylinder has previously been employed for
obtaining the desired mechanical advantage. Prior art powered
backup tongs are, however, generally complex with numerous moving
parts. Also, some powered backup tongs are not designed so that the
dies uniformly grip the tubular, thereby marring or otherwise
damaging the tubular. Oilfield tubulars including a chrome or other
protective coating and oilfield tubulars made from non-ferrous
materials are increasingly used in hydrocarbon recovery operations.
Both rotary tongs and backup tongs which will not mar these
tubulars are thus desired and have long been in demand.
One problem which is long plagued hydrocarbon recovery operations
is a difficulty associated with reliably making up and breaking
apart tubulars in a dual tubing string. Dual tubing strings are
typically provided on six inch centers, and most backup tongs
require that the tubing string be spread apart so that the backup
tong may be spaced between the dual tubulars. Extra time is
required to spread apart the tubulars when making up each
connection. Moreover, to enable the tubulars to be spread apart
sufficiently to accommodate the backup tong and the rotary tong,
the tongs generally must be positioned high above the rig floor,
thereby making the threaded and unthreaded operations more
difficult and time consuming.
The disadvantages of the prior art are overcome by the present
invention, and improved and relatively simple yet highly reliable
powered backup tong is hereinafter disclosed which overcomes these
and other problems associated with prior art tongs.
SUMMARY OF THE INVENTION
A suitable embodiment of a powered backup tong according to the
invention includes a single fluid powered cylinder spaced between
upper and lower cover plates which are part of the backup tong
body. A generally V-shaped wedge is mounted on the rod end of the
hydraulic cylinder assembly, and the cylinder assembly is arranged
so that rod extension presses the wedge away from the tubular. A
pair of links on opposing sides of the tong centerline are each
pivotally mounted on the backup tong body, and are engaged by the
wedge to move between a pipe release position and a pipe grip
position. A door jaw is pivotally mounted to each link. The pair of
door jaws move between an open position for laterally moving the
backup tong on and off the pipe, and a closed position wherein the
cantilevered ends of the door jaws may be latched together.
The backup tong includes three dies which each engage the tubular
along an arc of more than 90.degree., thereby together providing
substantially full circumferential die coverage of at least
270.degree.. One die is mounted on each of the movable door jaws. A
third die is provided on a third jaw which is either fixed to or
has limited movement with respect to the tong body and is spaced
radially opposite the open throat of the tong with respect to the
tubular gripped by the dies. The third jaw may be pressed into
engagement with the tubular by the cylinder end of the hydraulic
cylinder assembly.
According to the method of the invention, the door jaws are
initially in their open position so that the backup tong may be
moved laterally on and off the tubular and into engagement with the
third jaw. The door jaws are then closed and latched together with
a latch pin. Each of the three dies do not fully engage the tubular
at this stage, thereby facilitating easy latching of the door jaws.
The hydraulic cylinder assembly may then be activated at a selected
hydraulic pressure, thereby moving the wedge away from the pipe and
forcing each link outwardly from the tong centerline. This pivoting
movement of the links brings each of the door jaws into engagement
with the tubular. The cylinder activation simultaneously presses
the third jaw into engagement with the tubular. The angle of the
wedge and the resilience of the material between the cylinder
assembly and the third die may be selected to obtain the desired
compressive force on the tubular from each of the three dies. The
hydraulic cylinder assembly may then retract the wedge, thereby
releasing the dies from gripping engagement with the pipe. The
latch pin may then be removed and the door jaws moved to their open
position, thereby allowing the backup tong to be moved laterally
off the tubular string.
It is an object of the present invention to provide an improved
backup tong which utilizes a wedge powered by a fluid cylinder
assembly for simultaneously forcing multiple dies into gripping
engagement with the tubular. It is a further object of the
invention to provide an improved backup tong which has relatively
few moving parts, and which utilizes a design wherein the dies be
properly aligned for reliably gripping the tubular without marring
or otherwise damaging the tubular.
It is a feature of the present invention that a backup tong may
include three dies, with two of the dies being provided on opposing
door jaws which may be opened and closed about the tubular. The
door jaws may be closed and the cantilevered ends structurally
interconnected. A third jaw preferably is provided opposite the
throat of the backup tong relative to the oilfield tubular.
It is a further feature of the invention to provide a backup tong
with a pair of links which each pivot with respect to the tong
body. The links are moved in response to linear movement of a wedge
driven by the actuation of the cylinder assembly, thereby forcing
each of the dies into gripping engagement with the oilfield
tubular. In a preferred embodiment of the invention, the hydraulic
cylinder assembly and the wedge are arranged such that the wedge
moves away from the oilfield tubular, and each of the links move
laterally away from the centerline of the backup tong as the dies
are forced into gripping engagement with the tubular.
It is an advantage of the present invention that the backup tong
provides substantially full circumferential die coverage for
gripping engagement with the tubular. High biting forces may be
transmitted from the backup tong to the tubular utilizing dies with
extremely fine teeth, thereby preventing marring or other damage to
the tubular. It is a further advantage of the invention that the
backup tong is constructed such that the tong may be easily used to
make up and break apart dual tubular strings on relatively close
centers, with a minimal or no lateral spreading of the
tubulars.
These and further objects, features, and advantages of the present
invention will become apparent from the following detailed
description, wherein reference is made to the figures in the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top view of one embodiment of the backup tong according
to the present invention, illustrating the backup tong hydraulic
cylinder assembly in the pipe release position. The upper door jaw
is shown in the closed position and the lower door jaw is shown in
an open position for laterally moving the backup tong on and off a
tubular.
FIG. 2 is a cross-sectional view of the power tong as shown in FIG.
1 through lines 2--2 in FIG. 1.
FIG. 3 is a top view of a backup tong similar to the tong shown in
FIGS. 1 and 2. The hydraulic cylinder assembly has been activated
for bringing the dies into gripping engagement with the oilfield
tubular.
FIG. 4 is a top view of an alternate embodiment of a backup tong
according to the present invention. The backup tong on the top side
of the centerline in FIG. 4 is shown in gripping engagement with
the tubular, while the backup tong on the bottom side of the tong
centerline is shown in the pipe released position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 1 and 2 depict one embodiment of a backup tong 10 according
to this invention. The tong body 12 includes upper and lower cover
plates 14 and 16, respectively, which are structurally separated by
a pair of link pins 18 and 20 in the front end of the backup tong,
and by a rear block 22 and a pair of securing pins 24 and 26 at the
rear end of the tong. The upper cover plate 14 is removed in the
FIG. 1 illustration, and the configuration of the structurally
identical bottom cover plate is thus shown partially in dashed
lines in FIG. 1. The curved front portion 15 of each plate 14 and
16 is configured for receiving the tubular T within the tong. Also,
the tong body 12 may be provided with side plates between the cover
plates, although tong side plates which completely encapsulate the
inner components within the tong body 12 will have to be spaced
sufficiently from the centerline 28 to accommodate movement of the
links, as shown in FIG. 3.
A pair of links 30 and 32 are each mounted on the tong body 12 on
opposing sides of the tong centerline 28 and between plates 14 and
16, as shown in FIG. 2. Each pair of links may include an upper
link plate 34 and a lower link plate 36. The link plates are
vertically separated at their front end by a respective jaw block
or door jaw 38, 40, and at their rear end by a pair of rollers 42
each mounted on a pin 44 extending between the link plates 34 and
36. Each of the links 30 and 32 pivots with respect to the tong
body 12 about the respective link pivot pin 18, 20. Each of the
door jaws 38 and 40 are pivotally mounted to a respective link 30,
32 by one of the pair of jaw pivot pins 46, 48 which extend between
a respective pair of the link plates 34, 36. The rear end 50 of
each door jaw is thus spaced between a respective pair of link
plates 34, 36. The cantilevered front end 52 of each door jaw is
provided with an interlocking member 54 having an aperture 56
therein for receiving a latch pin 58. As shown in FIGS. 1 and 2,
the door jaw 40 has upper and lower interlocking members, and a
single latch member on the jaw 38 may thus fit in the recess 60
between these members so that the apertures 56 in each of the door
jaws may be aligned for receiving a common latch pin 58.
FIG. 1 depicts the jaw 40 in the open position and the jaw 38 in
the closed position. In practice, those skilled in the art will
understand that both the door jaws 38 and 40 may be opened so that
the backup tong may be moved laterally for placing the backup tong
on and off an oilfield tubular T extending vertically through a
well. Each of the door jaws 38, 40 include a die 62, 64 mounted
thereon, and another die 66 mounted on jaw 68 is provided opposite
the opened throat 70 of the backup tong. Those skilled in the art
will appreciate that the tong may be moved on and off the tubular
in a direction generally aligned with the centerline 28 of the
tong. Once the backup tong has been positioned so that the tubular
T engages the die 68, both the door jaws 38 and 40 may be closed,
and a pin 58 inserted through the apertures 56 in the pair of door
jaws so that the interconnected jaws and the tong body fully
encircle the tubular T. It should be understood that, in this
position, each of the jaws 62 and 64 typically will not engage the
tubular T, and instead a slight gap will exist between the dies 62,
64 and the tubular T, thereby facilitating the closing of both door
jaws 38, 40 and the positioning of the pin 50 for interconnecting
these jaws. A slight gap is thus depicted in FIG. 1 between the
closed door jaw die 62 and the tubular T. During this operation,
the cylinder 72 remains in its retracted position, as shown in FIG.
1.
Referring to FIGS. 1 and 3, a fluid powered cylinder assembly 72 is
provided between the cover plates 14 and 16, and laterally between
the links 30 and 32. Preferably a centerline of the cylinder
assembly 72 is aligned with the centerline 28 of the tong. The
cylinder portion 74 of the cylinder assembly may be structurally
secured to both the upper and lower cover plates 14 and 16 by
conventional securing members (not shown). The cylinder assembly is
provided with a rod end 76 which carries a wedge 80 thereon. The
rod end and the wedge are linearly movable along the centerline 28
of the tong, and preferably are arranged such that the rod 76
extends from the cylinder body 74 to move the wedge 80 away from
the tubular T when the cylinder assembly 72 is activated for
gripping the tubular. The wedge 80 is provided with tapered camming
surfaces 82 and 84 which each engage a respective roller 42 mounted
at the rear end of a respective link 30, 32 when activating the
cylinder assembly 72. The wedge 80 thus pivots the links 30 and 32
about the pivot pins 18 and 20, and drives each of the links 30 and
32 outward from the centerline 28, as shown in FIG. 3.
According to one embodiment of the invention, as shown in FIG. 1,
the cylinder housing 72 is fixed to the tong plates 14, 16, and the
jaw 68 is similarly fixed between the cover plates 14 and 16.
According to another embodiment, as shown in FIG. 3, the cylinder
assembly 72 is spaced between the tong plates 14 and 16 so that it
is maintained on the centerline 20, although the cylinder assembly
is free to move in a direction along the centerline 28. According
to this alternate embodiment as shown in FIG. 3, the jaw 68 is
similarly mounted between the cover plates 14 and 16 in a manner
such that limited movement of the jaw 68 in a direction along the
axis 28 is possible. In this embodiment, a resilient material
sleeve 86 is mounted on a pin 88 which extends between the cover
plates 14 and 16. Pin 88 is fixed to the jaw 68, and slides within
a short slot (not depicted) in both the upper and lower cover
plates 14 and 16 for allowing limited movement of the fixed jaw 68
and thus the die 66 thereon in a direction along centerline 28.
During activation of the cylinder assembly 72, the cylinder body 70
may press against the resilient material sleeve 86, while the wedge
80 simultaneously forces the links 30 and 32 outward, as shown in
FIG. 3. By allowing the rear end of the cylinder assembly 72 to
press against the resilient sleeve 86, limited movement of the jaw
68 is possible, thereby allowing the die 66 to move slightly to
increase its gripping force on the tubular T.
Once the cylinder assembly 72 has been activated, it may be seen
that the lateral movement of the links 30 and 32 brings each of the
door jaws 38 and 40 inwardly toward the central axis 90 of the
tubular T, thereby bringing each of the jaws 62, 64 and 66 into
gripping engagement with the tubular T. During this operation, the
pin 58 also functions as a hinge to allow each of the dies 62, 64
and 66 to achieve a biting engagement with the tubular T without
marring or damaging the tubular. Relatively fine teeth may be
provided on each of the dies for gripping engagement with the
tubular. Preferably each of the dies 62, 64 and 66 occupies a
circumferential length of at least 90.degree. for engaging the
tubular, so that the circumference of the three dies in engagement
with the tubular is greater than 270.degree., and preferably is
greater than 300.degree. when the dies grip the tubular, as shown
in FIG. 3. The design of the backup tong 10 as described herein
achieves a very tight grip on the tubular utilizing a single
cylinder assembly, and includes relatively few moving parts.
Cylinder assembly 72 may be activated in response to either air or
hydraulic fluid, although preferably hydraulic fluid is used to
activate the cylinder assembly. When pressure is applied to the
cylinder assembly 72, the rod 76 extends from the cylinder body 74
so that the wedge moves each of the links laterally outward and
tightens the door jaws against the tubular. To disconnect the
backup tong 10 from gripping engagement with the tubular, hydraulic
fluid is applied to the cylinder assembly 72 to retract the rod 76
and return the wedge to the position as shown in FIG. 1. The pin 58
may then be easily removed from the jaw doors 38, 40, and the doors
each moved to an open position so that the tong may be moved
laterally off the tubular T.
By positioning the cylinder assembly so that the wedge 80 moves in
a direction away from the tubular T when gripping the tubular, the
mechanical advantage of the links 30 and 32 is maximized without
increasing the size of the tong. The pivot pins 18 and 20 are thus
preferably spaced toward the front end of the tong body 12, and
force is applied to the rear end of the links 30 and 32 through the
wedge 80. The front end of end link 30, 32 is thus forced slightly
toward the centerline 28. The door jaws 38 and 40 are pivotally
connected to the front end of the links, and thus are driven toward
the central axis 90 of the tubular T to bring the dies into biting
engagement with the tubular T. Also, the arrangement as shown in
FIG. 3 allows both the cylinder rod 76 and the cylinder body 74 to
be functionally used to assist in biting engagement of the dies
with the pipe, as explained above.
The block 22 also functions as a stop for engaging the end 92 of
the wedge 80, thereby preventing application of too much biting
force on the tubular T. Those skilled in the art will appreciate
that the cam sides 82 and 84 of the wedge 80 may be configured for
increasing or decreasing the biting force applied by the dies 62
and 64. Due to the substantial mechanical advantage obtained by the
arrangement of the links 30 and 32 as disclosed herein, each of
these cam wedges according to the present invention may have a
substantially large cam angle of from about 20.degree. to
40.degree. with respect to the centerline 28 of the backup tong.
According to the preferred embodiment of the invention, the camming
angle of the sides 82 and 84 of the wedge 80 is arranged at from
about 27.degree. to about 33.degree. with respect to the centerline
28 of the tong.
A significant advantage of the embodiments as shown in FIGS. 1 and
3 is that the tong 10 may operate with a very small space provided
between the tubular T and another tubular, which may be positioned
adjacent either the door jaw 38 and the door jaw 40 and between the
pins 58 and 46 or 48, respectively. The tong as shown in FIGS. 1
and 3 may thus be laterally moved to engage one tubular therein,
while a second tubular T2, as shown in dashed lines in FIG. 3, is
provided adjacent the gripped tubular. At least one and preferably
both the door jaw 38 and 40, is configured such that the door jaw
has a relatively thin body portion between the respective pivot 46,
48 and the door latch device 58. The relatively thin portion of the
door jaw has a body thickness which is less than 3 inches, and
preferably less than about 2.5 inches, so that another tubular may
be positioned immediately exterior of the closed and latched door
jaw, as shown in FIG. 3. The backup tong 10 is thus well suited for
use in dual tubing strings, wherein the lateral spacing between the
centerline of the dual tubulars is six inches or only slightly
greater than six inches. This design accordingly allows the tong to
be easily moved on and off the tubular, as disclosed herein.
FIG. 4 discloses an alternate embodiment of a backup tong 110 with
a tong body 112 which includes upper and lower tong plates as
discussed above. Again, the upper tong plate has been removed in
the FIG. 4 illustration, and the outline of the lower tong plate
116 is depicted.
In the FIG. 4 embodiment, the cylinder assembly 172 is mounted
within the body 112 with the cylinder housing 174 fixed to the rear
block 122. The rod end 176 thus projects inwardly toward the
tubular T when the cylinder assembly is activated for gripping
engagement with the tubular. A pair of links 130 and 132 are
provided on opposing sides of the tong centerline 128 and pivot
about link pivot pins 118 and 120 secured between the tong plates.
The wedge 180 at the end of the rod 176 includes a pair of first
tapered surfaces 181 and 183 which have a very high cam angle for
initially bringing the dies toward engagement with the pipe. Wedge
80 also has a pair of lower cam angle surfaces 182 and 184 which
function to bring the dies into final gripping engagement with the
pipe. In a suitable embodiment, the surfaces 181 and 183 may be
angled at approximately 45.degree. relative to the centerline 128,
while the surfaces 182 and 184 ar each inclined at a lower and thus
more powerful cam angle of from 6.degree. to about 10.degree..
A roller 142 is fixed to the rear end of each link 130 and 132, and
engages the wedge 118 in a manner previously described for rollers
42. When the cylinder assembly 172 is activated, the wedge forces
the rear end of each link 130, 132 laterally outwardly from the
centerline 128, thereby pivoting each link about a respective pin
118, 120 and forcing each of the dies 162 and 164 into gripping
engagement with the tubular T.
Head 168 is fixed to the tong body, and supports die 166 thereon. A
jaw block 139 and 141 is pivotally mounted on the front end of each
of the links 130 and 132 by a respective pin 146 and 148. The pin
allows each of the jaw blocks 139 and 141 to rotate slightly,
thereby allowing each die 162 and 164 to become perfectly aligned
for gripping engagement with the tubular T. By allowing each die
162 and 164 to pivot slightly with respect to the respective link
130 and 132, each of the three dies 162, 164 and 166 may become
properly aligned for gripping engagement with the tubular without
marring or damaging the tubular.
The design as shown in FIG. 4 is well suited for tongs designed for
engaging large diameter tubulars where the space allows for larger
jaws. The advantage of the design as shown in FIG. 4 is that the
jaws tightly grip the tubular without the need for a door latch.
The FIG. 4 design, like the previously described designs, is
relatively simple and has few parts. Each of the dies may be
perfectly aligned with the tubular. Additional links and additional
cylinders are not required to open and close doors or force the
dies into gripping engagement with the tubular.
For each of the embodiments described herein, each of the links,
the door jaws and the jaw blocks is preferably pivotally connected
to its respective support member by a pivot pin. High reliability
and trouble free operation of the tong are obtained, at least in
part, by not utilizing slots or similar arrangements which provide
"play" between these components to enable the dies to engage the
tubular. Each pivot pin thus allows for rotation of one component
about the other and movement between these respective components is
practically limited to rotational movement.
Although the invention has thus been described in detail for
certain embodiments, it should be understood that this explanation
is for illustration, and that the invention is not limited to these
embodiments. Alternative equipment and operating techniques will
thus be apparent to those skilled in the art. In view of this
disclosure, modifications are thus contemplated and may be made
without departing from the spirit of the invention, which is
defined by the claims.
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